Transcription factor Pit-1 expression is modulated upon seasonal acclimatization of eurythermal ectotherms: Identification of two Pit-1 genes in the carp

Abstract

A second Pit-1 gene in carp (Cyprinus carpio), including the complete structural gene and 1.1 kb of promoter region, was identified and completely sequenced. The exon-intron structure was determined, and reverse transcription-polymerase chain reaction (RT-PCR) experiments suggest that only one Pit-1 splice variant is present in carp pituitary. The effect of seasonal acclimatization on the extent of Pit-1 gene expression was studied in summer- and winter-acclimatized carp. Quantitative RT-PCR analysis revealed a clear increase of Pit-1 mRNA in the pituitaries from summer-acclimatized carp compared with the winter-adapted fish. In situ hybridization of pituitary gland sections with riboprobes representing the complete 5'-transactivating region of carp Pit-1 depicted a significantly higher Pit-1 mRNA level in the rostral pars distalis of the summer-acclimatized fish where prolactin is expressed in a manner that resembles the seasonal increase observed in the proximal pars distalis and the pars intermedia. The cell- and temporal-specific transcription of Pit-1 supports its role in the molecular mechanisms that underly the acclimatization process undergone by eurythermal fish as a result of the physical effects of seasonal changes on their habitat.

Eurythermal fish acclimatization and nucleolar function: a review

“…Although acclimatization and acclimation show some distinctive features (Segner and Braunbeck, 1990), both require molecular and gene expression adjustments to provide the homeostatic condition that fish need to survive. As a natural physiological process, acclimatization is genetically programmed and involves a recurring seasonal reprogramming of molecular and cellular functions along with a modulation of transcriptional and translational events (On˜ate et al, 1987;Vera et al, 1993Vera et al, , 1997Figueroa et al, 1994;Kausel et al, 1999;Sarmiento et al, 2000). Acclimation also entails differential gene expression (Segner and Braunbeck, 1990;Goldspink, 1995;Tiku et al, 1996;Hirayama and Watabe, 1997;Figueroa et al, 1997;Hirayama et al, 1998;Arends et al, 1998;Ju et al, 2002).…”

Environmental acclimatization of the carp modulates the transcription of ?-actin

“…The conditions for reverse transcription with Superscript II RT (Gibco-BRL, St. Louis, MO) and the 30 cycles of amplification with Taq DNA polymerase (93°C for 1 min, 55°C for 1 min, and 72°C for 90 s) were essentially those described by Kausel et al [1999]. The reaction yielded a single amplification product of aproximately 1,800 bp, which was ligated to the TA-cloning vector pCR2.1 (Invitrogen, La Jolla, CA).…”

“…When reverse transcribed carp RNA was the template, a product of 282 bp was attained, while genomic DNA yielded a fragment of 383 bp containing the sequence of intron V. A competitive ␤-actin DNA was constructed as reported by Kausel et al [1999], except that the 412 bp HindIII-EcoRI-fragment of a carp ribosomal RNA clone was ligated to the oligonucleotides ␤act2942se and ␤act3305an and the phosphorylated complementary oligonucleotides 5Ј-AGCTCAGTGTTGGCATACAGGTCC3-3Ј and 5Ј-AATTTGTTACCACTTCACGCCGAC-3Ј harboring HindIII-or EcoRI-compatible ends, respectively. The resulting competitive ␤-actin DNA was further amplified using ␤act2942se and ␤act3305an as primers, and dilutions were prepared in 50 g/ml glycogen.…”

“…Acclimation, although a distinctive process [Segner and Braunbeck, 1990], also requires molecular and gene expression adjustments to provide the homeostatic condition that fish need to survive [Segner and Braunbeck, 1990;Goldspink, 1995;Tiku et al, 1996;Hirayama and Watabe, 1997;Hirayama et al, 1998;Arends et al, 1998]. Current research on the complex physiological adaptive mechanisms underlying fish acclimatization and acclimation includes: 1) studies on the neuroendocrine cascade triggered by changes in ambient temperature, which at the same time entails transcriptional modulation in the hypothalamic-pituitary axis Arends et al, 1998;Kausel et al, 1999]; 2) assessment of muscle [Goldspink, 1995;Hirayama and Watabe, 1997] and cell membrane fluidity responses [Tiku et al, 1996] associated with the regulation of the expression of specific genes; and 3) the characterization of the molecular events that sustain the generalized nucleolar rearrangement which reveal profound changes in ribosomal biogenesis as a consequence of the seasonal environmental variations [Vera et al, 1993Kausel et al, 1999].…”

Temperature influence on key players of the somatotropic axis of tench, Tinca tinca (Actinopterygii: Cypriniformes: Cyprinidae)

“…In several fi sh species higher GH concentrations in blood were reported during night and what might have been correlated with higher melatonin levels (Falcón et al 2003). Kausel et al (1999) presented that water temperature had a great impact on GH levels in samples of common carp, Cyprinus carpio Linnaeus, 1758.…”